There is no way to do this (that I know of, I could be corrected and learn something as well) unless you've installed a package to handle this. Meaning, if you didn't plan ahead and monitor a file, there is no way to get this information. All you'll be able to get from the file is the basic information that the stat <filename> cmd shows you, which wont show you what user altered a file.

That being said, in the future there are packages like audit that help you handle this and after you set a file to be audited, a simple ausearch -f <filename> would allow you to see this type of information.
You could also use something like aide -- which I personally like.